This application is based upon and claims the benefit of priority from the prior Japanese Patent Applications No. 2000-133516, filed May 2, 2000; and No. 2001-003923, filed Jan. 11, 2001, the entire contents of both of which are incorporated herein by reference.
The present invention relates to a developing apparatus having a toner container for storing toner and a developing roller incorporated in the toner container, and to an electronic photographing apparatus, such as a laser printer or a copying machine, incorporating the developing apparatus. More specifically, the present invention relates to a structure for preventing toner from spilling from the toner container, when the toner pressure in the toner container is increased.
An electronic photographing apparatus, such as a laser printer, comprises a photosensitive drum having a surface on which an electrostatic latent image is formed, a developing apparatus for developing the electrostatic latent image to a toner image, and a transferring apparatus for transferring the toner image to a recording paper sheet.
The developing apparatus for use in this type of electronic photographing apparatus has a toner container for storing toner. The toner container has an opening portion, which faces the photosensitive drum. A developing roller and a developing plate are located in the opening portion. The developing roller is arranged parallel to the photosensitive drum. The developing roller incorporates a magnet roller. Owing to the magnetic force of the magnet roller, toner is attracted to the peripheral surface of the developing roller. As the developing roller rotates, the toner adhered to the peripheral surface of the developing roller is guided to a developing position between the developing roller and the photosensitive drum.
The function of the developing plate is to make a toner layer adhered to the peripheral surface of the developing roller uniform in thickness. The developing plate is arranged at a position opposite from the developing position in the direction of rotation of the developing roller.
With the developing apparatus described above, the toner adhered to the peripheral surface of the developing roller is first guided to the developing plate as the developing roller rotates, and excess toner is scraped off by the plate. As a result, a thin uniform toner layer is formed on the peripheral surface of the developing roller. The toner layer is guided to the developing position by the rotation of the developing roller, and adhered to the surface of the photosensitive drum at this position. Consequently, the electrostatic latent image on the surface of the photosensitive drum is developed, so that a toner image is formed on the surface.
In the conventional developing apparatus, the toner container has a bottom wall for receiving toner. The bottom wall has an end portion facing the opening portion. The end portion of the bottom wall is located under the developing roller and faces the peripheral surface of the developing roller. A gap is provided between the end portion of the bottom wall and the peripheral surface of the developing roller for the following reason.
Even after the toner passes through the developing position, part of the toner is kept attracted to the peripheral surface of the developing roller and remains on the surface. The remaining toner is returned to the opening portion of the toner container as the developing roller rotates.
At this time, if there is no gap between the developing roller and the bottom wall of the toner container, the toner remaining on the developing roller is brought into contact with the bottom wall at the opening portion, and removed from the peripheral surface of the developing roller. The removed toner is accumulated in the end portion of the bottom wall and cannot be returned into the toner container. Therefore, the amount of toner accumulated in the end portion of the bottom wall is increased with the passage of time, resulting in the drawback that the toner is scattered out of the toner container through the opening portion.
For the reason described above, according to the conventional developing apparatus, a gap is positively provided between the bottom wall of the toner container and the developing roller to avoid contact between the toner remaining on the peripheral surface of the developing roller and the bottom wall, thereby preventing scattering of the toner.
In the case where there is a gap between the bottom wall of the toner container and the developing roller, it is inevitable that part of the toner contained in the toner container will enter the gap. The toner in the gap is influenced by the magnetic force of the magnet roller and attracted to the peripheral surface of the developing roller in a normal image forming operation. Therefore, the toner in the gap is never scattered or spilt out of the toner container.
However, if the developing apparatus receives shock, for example, when the developing apparatus is set to the electronic photographing apparatus, the pressure of the toner contained in the toner container may be temporarily increased. This pressure may be exerted on the gap. Further, when the toner container is replenished with new toner, the new toner put in the toner container drops on the existing toner. Therefore, this shock may increase the pressure of the toner in the toner container. This pressure may be exerted on the gap.
In this case, the toner attracted to the peripheral surface of the developing roller at the position of the gap or the toner located near the gap may be pushed out from the toner container. This results in the problems that the toner is scattered around the toner container, contaminates the interior of the electronic photographing apparatus or adheres to recording paper.
An object of the present invention is to provide a developing apparatus and an electronic photographing apparatus, in which although there is a gap between a toner supplying body and a bottom wall of a toner container, toner is prevented from spilling out through the gap.
To achieve the above object, a developing apparatus according to a first aspect of the present invention comprises: a toner container for storing toner, the toner container having a bottom wall for receiving the toner and an opening formed at an end portion of the bottom wall and facing a photosensitive body on which an electrostatic latent image is formed; a toner supplying body located at the opening of the toner container, the toner supplying body having a peripheral surface which is exposed in the toner container and to which the toner is adhered, for supplying the toner adhered to the peripheral surface to the photosensitive body by rotation, a gap being formed between the peripheral surface and the bottom wall to return toner remaining on the peripheral surface of the toner supplying body to the toner container; and a toner restricting portion projected upward from the bottom wall of the toner container, the toner restricting portion facing the gap at a position a distance from the gap to be inside the toner container.
In the above structure, if the toner container receives a shock or is replenished with new toner, the pressure of the toner in the toner container is increased. Due to the increase in pressure, the toner near the gap is liable to be pressed out through the gap. However, since the toner restricting portion faces the gap in the toner container, it can receive, immediately upstream from the gap, the pressure of the toner which is exerted toward the gap.
Therefore, the toner held by the toner supplying body and facing the gap or the toner existing near the gap is not pressed out of the toner container. Thus, the toner can be prevented from scattering out of the toner container.
To achieve the above object, a developing apparatus according to a second aspect of the present invention comprises: a toner container for storing toner, the toner container having a bottom wall for receiving the toner and an opening formed at an end portion of the bottom wall and facing a photosensitive body on which an electrostatic latent image is formed; a toner supplying body located at the opening of the toner container, the toner supplying body having a peripheral surface which is exposed in the toner container and to which the toner is adhered, for supplying the toner adhered to the peripheral surface to the photosensitive body by rotation, a gap being formed between the peripheral surface and the bottom wall to return toner remaining on the peripheral surface of the toner supplying body to the toner container; and a toner restricting portion projected upward from the bottom wall of the toner container, the toner restricting portion facing the gap at a position a distance from the gap to a side of the photosensitive body.
In the above structure, if the toner container receives a shock or is replenished with new toner, the pressure of the toner in the toner container is increased. Due to the increase in pressure, the toner near the gap is liable to be pressed out through the gap. However, since the toner restricting portion faces the gap from the side of the photosensitive body, even if the toner flows into the gap, the flow of the toner is blocked at the position of the toner restricting portion.
Therefore, the toner held by the toner supplying body and facing the gap or the toner existing near the gap is not pressed out of the toner container. Thus, the toner can be prevented from scattering out of the toner container.
To achieve the above object, a developing apparatus according to a third aspect of the present invention comprises: a toner container for storing toner, the toner container having a bottom wall for receiving the toner and an opening formed at an end portion of the bottom wall and facing a photosensitive body on which an electrostatic latent image is formed; a toner supplying body located at the opening of the toner container, the toner supplying body having a peripheral surface which is exposed in the toner container and to which the toner is adhered, for supplying the toner adhered to the peripheral surface to the photosensitive body by rotation, a gap being formed between the peripheral surface and the bottom wall to return toner remaining on the peripheral surface of the toner supplying body to the toner container; and first and second toner restricting portions projected upward from the bottom wall of the toner container and facing the gap with the toner supplying body interposed therebetween.
In the above structure, if the toner container receives a shock or is replenished with new toner, the pressure of the toner in the toner container is increased. Due to the increase in pressure, the toner near the gap is liable to be pressed out through the gap. However, since one of the first and second toner restricting portions faces the gap in the toner container, it can receive, immediately upstream from the gap, the pressure of the toner that is exerted toward the gap. As a result, increase in pressure near the gap can be prevented. Since the other toner restricting portion faces the gap from the side of the photosensitive body, even if the toner flows into the gap, the flow of the toner is blocked at the position of the other toner restricting portion.
Therefore, when the toner held by the toner supplying body and facing the gap or the toner existing near the gap is liable to be pressed out of the toner container, it can be blocked by the two toner restricting portions provided on both sides of the toner supplying body. Thus, it is particularly ensured that the toner is prevented from scattering out of the toner container.
To achieve the above object, an image processing unit of the present invention comprises: a photosensitive body on which an electrostatic latent image is formed; and a developing apparatus to be brought into combination with the photosensitive body. The developing apparatus comprises: a toner container for storing toner, the toner container having a bottom wall for receiving the toner and an opening formed at an end portion of the bottom wall and facing the photosensitive body; a toner supplying body located at the opening of the toner container, the toner supplying body having a peripheral surface which is exposed in the toner container and to which the toner is adhered, for supplying the toner adhered to the peripheral surface to the photosensitive body by rotation, a gap being formed between the peripheral surface and the bottom wall to return toner remaining on the peripheral surface of the toner supplying body to the toner container; and at least one toner restricting portion projected upward from the bottom wall of the toner container, the toner restricting portion facing the gap at one of a position a distance from the gap to be inside the toner container and a position a distance from the gap to a side of the photosensitive body.
Further, to achieve the above object, an electronic photographing apparatus comprises: an apparatus body having a transfer path through which a sheet-like recording medium is transferred; a photosensitive body which is arranged in the transfer path and on which an electrostatic latent image is formed; and a developing apparatus for causing toner adhered to the electrostatic latent image, thereby forming a toner image. The developing apparatus comprises: a toner container for storing the toner, the toner container having a bottom wall for receiving the toner and an opening formed at an end portion of the bottom wall and facing the photosensitive body; a toner supplying body located at the opening of the toner container, the toner supplying body having a peripheral surface which is exposed in the toner container and to which the toner is adhered, for supplying the toner adhered to the peripheral surface to the photosensitive body by rotation, a gap being formed between the peripheral surface and the bottom wall to return toner remaining on the peripheral surface of the toner supplying body to the toner container; and at least one toner restricting portion projected upward from the bottom wall of the toner container, the toner restricting portion facing the gap at one of a position a distance from the gap to be inside the toner container and a position a distance from the gap to a side of the photosensitive body.
In the above structure, if the toner container receives a shock or is replenished with new toner, the pressure of the toner in the toner container is increased. Due to the increase in pressure, the toner near the gap is liable to be pressed out through the gap.
However, if the toner restricting portion is provided at the position facing the gap in the toner container, it can receive, immediately upstream from the gap, the pressure of the toner that is exerted toward the gap. As a result, increase in pressure near the gap can be prevented. If the toner restricting portion is provided at the position facing the gap from the side of the photosensitive body, even if the toner flows into the gap, the flow of the toner is blocked at the position of the toner restricting portion. Further, if the two toner restricting portions are provided at both the position facing the gap in the toner container and the position facing the gap from the side of the photosensitive body, when the toner is liable to be pressed out of the toner container, it can be blocked by the two toner restricting portions provided on both sides of the toner supplying body.
Thus, the toner is prevented from scattering out of the toner container, and the problem of contamination of the photosensitive body, the apparatus body or the recording medium can be solved.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.